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Brighton and Hove City Council England

LAQM Detailed Assessments 2012 1

Air Quality Detailed Assessment for Rottingdean Village Preston Road and The Drove



Local Authority Officer Samuel Rouse

Department Environmental Health and Licensing

Address

Environmental Protection Team Bartholomew House Bartholomew Square Brighton BN1 1JP

Telephone 01273 292256 e-mail [email protected] Report Reference number

BHCC Detailed Assessments 2012

Date November 2012



Executive Summary In 2008 Brighton and Hove City Council (BHCC unitary authority) declared a

centralised Air Quality Management Area (AQMA) for none compliance of

nitrogen dioxide (EU and English legal limits - hourly and annual). This report

considers if areas outside of the existing AQMA are compliant with nitrogen

dioxide limits for the protection of human health.

In 2008/09 Defra (Department of Environment Food And Rural Affairs) requested

that the city council carry out roadside nitrogen dioxide monitoring outside of the

cities 2008-AQMA. This commenced in January-2009 with further sties added in

2010 including diffusion tube monitors in three new areas; Portslade Old Village,

Preston Road Preston Drove junction and Rottingdean Village. As a

complementary line of enquiry the 2010 further assessment extended detailed

dispersion modelling to a number of areas adjacent to the existing AQMA.

Work over the past four years; has established that nitrogen dioxide is likely to be

compliant in the following areas:

• Falmer and the A27 corridor - considered with screening tool assessment

methods

• Five Dials Junction - assessed with ADMS-urban modelling as a part of the

2010 further assessment, nitrogen dioxide concentrations deemed to be

well below objectives levels

• Portslade Old Village - the monitor adjacent to South Street demonstrated

much lower concentrations than the objective and this was backed up by

detailed dispersion modelling carried out for the last further assessment.

These areas have all ready been considered as part of the Local Air Quality

Management (LAQM) process and do not require further air quality assessment

at this time. In contrast nitrogen dioxide monitoring suggests concentrations

continue to exceed the annual mean objective in or near to:



• Preston Road Preston Drove Junction and The Drove

• Rottigndean Village

Therefore defra agreed that there is a need to carry out detailed air quality

assessments for these two general areas in accordance with the best available

technical guidance. For simplicity the two separate assessment areas for

nitrogen dioxide are included in this one report.

The Updating Screening Assessment and these detailed assessments 2012

conclude that the existing AQMA requires a review. The Preston Road and

Rottingdean areas should be included in a new AQMA. It is recommended that

the cities air quality model be updated and a new AQMA map produced. The

new 2013 quality action plan will target the new AQMA with recommendations

justified by evidence presented in the most up to date technical investigations.



Table of Contents Executive Summary .............................................................................................................................3 Table of Contents................................................................................................................................5 List of Tables.........................................................................................................................................6 List of Figures........................................................................................................................................7

Glossary.............................................................................................................................................7 1 Introduction .................................................................................................................................8

1.1 Brighton and Hove City Council....................................................................................8 1.1.1 The Existing AQMA......................................................................................................8 1.1.2 Rottingdean ....................................................................................................................9 1.1.3 Preston Road-Preston Road junction and South Road to the Drove............ 10

1.2 Purpose of Local Air Quality Management............................................................... 10 1.2.1 Reason for Detailed Assessments .......................................................................... 11

1.3 Air Quality Objectives................................................................................................... 11 1.3.1 Discussion about Nitrogen Dioxide objectives................................................... 11

2 Methodology ............................................................................................................................. 13 2.1 Monitoring Method ........................................................................................................ 13

2.1.1 Diffusion Tubes........................................................................................................... 13 2.1.2 Model Assessment Methodology............................................................................ 15 2.1.3 Model Approach - Year ............................................................................................ 15 2.1.4 Model Approach Emission Calculation.................................................................. 16 2.1.5 Model Approach - after emission variables.......................................................... 16 2.1.6 Traffic Data.................................................................................................................. 17 2.1.7 Traffic Speed................................................................................................................ 18 2.1.8 Road Width ................................................................................................................. 19 2.1.9 Road Gradient............................................................................................................. 19 2.1.10 Emission Factors .................................................................................................... 20 2.1.11 Street Canyons....................................................................................................... 20 2.1.12 Selected Model Receptors................................................................................... 20 2.1.13 Industrial Sources .................................................................................................. 21 2.1.14 Commercial and Domestic Emissions............................................................... 21 2.1.15 Ambient Background Levels................................................................................ 21 2.1.16 Chemistry................................................................................................................ 22 2.1.17 Meteorological Data ............................................................................................. 22 2.1.18 Time Varying Emissions........................................................................................ 22 2.1.19 Latitude and Sunlight............................................................................................. 23 2.1.20 Local Surface Parameters..................................................................................... 24 2.1.21 Model Performance and Uncertainty ................................................................ 24

3 Results ........................................................................................................................................ 26 3.1 Monitoring Results ......................................................................................................... 26

3.1.1 Model Verification...................................................................................................... 26 3.2 Results of Modelling Predictions ................................................................................. 26

3.2.1 Sensitivity Analysis ..................................................................................................... 26 3.2.2 Results at Receptors.................................................................................................. 27 3.2.3 Contour Map Results ................................................................................................ 27

3.3 Discussion of Results ..................................................................................................... 27 4 Conclusions............................................................................................................................... 28 5 Future Work and Recommendations ................................................................................. 29



6 Action Plan Options................................................................................................................ 30 7 References................................................................................................................................. 31 8 Appendix.................................................................................................................................... 32

List of Tables Table 1-1 Nitrogen Dioxide Air Quality Objectives Included in Regulations for the purpose of LAQM in England......................................................................................................... 11 Table 8-1 Nitrogen Dioxide Monitors in the Detailed Assessment Areas ......................... 32 Table 8-2 List of Model Receptor Points Preston Drove Detailed Assessment Area..... 34 Table 8-3 List of Model Receptor Points Rottingdean Detailed Assessment Area ........... 36 Table 8-4 2010 Traffic Counts for Preston Road Area AADT (Annual Average Daily Traffic) ................................................................................................................................................. 41 Table 8-5 2010 Traffic Counts for Rottingdean AADT ........................................................... 41 Table 8-6 Preston Road Area Road Link Parameters............................................................... 44 Table 8-7 Rottingdean Road Link Parameters............................................................................ 44 Table 8-8 Preston Road Area - Road Link Emission Rates (ranked top first) .................... 47 Table 8-9 Rottingdean Road Links emissions rates................................................................... 48 Table 8-10 Model Verification for Preston Road Area – model predictions compared with annual monitoring.................................................................................................................... 50 Table 8-11 Model Verification for Rottingdean Area best fit scenario................................. 50 Table 8-12 Model Results (NO2) for Preston Road Area Receptor Points highest first.. 51 Table 8-13 Model Results (NO2) for Rottingdean Area Receptor Points ........................... 52



List of Figures Figure 1-1 Brighton and Hove AQMA and Green Space (2008-2012) and 2012 Detailed Assessment Areas................................................................................................................................9 Figure 2-1 Nitrogen Dioxide Monitoring in or adjacent to the Detailed Assessment Areas.................................................................................................................................................... 14 Figure 2-2 Vehicles Specific Power relates to emission rates................................................. 16 Figure 2-3 Twenty-Four hour Traffic Variability A259 Brighton............................................ 23 Figure 8-1 Map of Model Receptor Points Preston Road Detailed Assessment Area...... 33 Figure 8-2 Map of Receptor Points Rottingdean Detailed Assessment Area ..................... 35 Figure 8-3Continuous Traffic Counter Information (Available for Rottingdean Only courtesy of the Transport Authority).......................................................................................... 38 Figure 8-4 Cross Sectional View of Rottingdean High Street and the Drove..................... 46 Figure 8-5 Local Wind Rose for Shoreham by Sea 2008 (Left) compared with 2010 (Unavailable for Gatwick data)....................................................................................................... 49 Figure 8-6 Model Results Contoured for Preston Road Area ............................................... 54 Figure 8-7 Model Results Contoured for Rottingdean Area .................................................. 55

Glossary µg/m3 Concentration micrograms per cubic metre 2WP Two Wheel Powered Vehicles - motorbikes, mopeds and scooters ADMS Atmospheric Dispersion Model System from CERC AHGV Articulated Heavy Goods Vehicle AQMA Air Quality Management Area AURN Automatic Urban Rural air monitoring Network (UK) BH9 Brighton and Hove 9 monitor BHCC Brighton and Hove City Council CAPP Continuous Analyser Preston Park AURN CERC Cambridge Environmental Research Consultants Defra Department of the Environment Food and Rural Affairs EMIT Emission Inventory Tool from CERC HGV Heavy Goods Vehicle LAQM Local Air Quality Management Area LGV Light Goods Vehicle m/sec velocity metres per second NO2 Nitrogen Dioxide PD Preston Drove Preston Road area PSV Passenger Service Vehicles - coaches and buses RHGV Rigid Heavy Goods Vehicle RR Rottingdean Receptors



1 Introduction

1.1 Brighton and Hove City Council

Brighton and Hove City Council (BHCC) is the majority constituent of the

Brighton-Worthing-Littlehampton agglomeration in Sussex on the South Coast of

England. The 2011 census indicates that the cities population rose by more than

10% since the previous census in 2001, to 273,400 residents early 20111. At a

similar rate of increase the population is expected to be approximately 287,000 by

the end of 2015. The urban area between the South Downs National Park and

the English Channel has a population density similar to many London Boroughs.

It is estimated that approaching half a million inhabitants live across four Sussex

authorities between Peacehaven in the east and Littlehampton in the west. A

reasonable assumption for vehicle ownership is one vehicle for every two people.

Therefore we estimate there are approximately 240,000 vehicles in the Brighton-

Worthing-Littlehampton conurbation. In contrast much of the council area is part

of the South Downs National Park where population densities are amongst the

lowest in South East England. Under Part IV of the Environment Act 1995 BHCC

declared an Air Quality Management Area AQMA (in 2008) of 1,060 hectares

(2,600 acres) for none compliance of Nitrogen Dioxide (NO2) objectives (annual

mean and hourly).

1.1.1 The Existing AQMA

Brighton and Hove’s second AQMA was declared in 2008 for both nitrogen

dioxide hourly and annual mean objectives. The 2008-AQMA declared under

Part IV of the Environment Act 1995 extends from Arundel Road in the east to

Adur District Council in the west, up to but not including Preston Park and the Old

Shoreham Road to the north and to the English Channel in the south. The AQMA

is approximately 12 % of BHCC’s administrative area as Figure 1-1. The

2008 AQMA does not include the South Downs National Park (green) or

substantial residential areas to the north and east of the city centre. The zone

that actually exceeds the NO2 annual mean objective is typically within ten metres

(potentially fifteen in exceptional cases) of certain narrow or confined road

1 Reference to the 2011 Census Results http://www.brightonbusiness.co.uk/htm/ni20120717.660827.htm



carriageways and is actually considerably less than the broader AQMA envelope.

The map below also depicts the position of the two detailed assessment areas

adjacent to the existing AQMA.

Figure 1-1 Brighton and Hove AQMA and Green Space (2008-2012) and 2012 Detailed Assessment Areas

1.1.2 Rottingdean Rottingdean is a coastal village to the east of Brighton. It is within Brighton and

Hove City council’s administrative area with its own parish council. The village

has a population of around 2,900 approximately 1% of the unitary authority. The

South Downs National Park surrounds the village and separates it from The

Marina and Brighton’s urban centre to the west. Many of the buildings flanking

Rottingdean High Street and adjoining Vicarage Lane were built centuries before

motorised traffic started to become popular in the 1920s. Street pavements are

narrow and some residential facades are 45 cm (16 inches) from the road

carriageway. The B2123 runs through the centre of Rottingdean village and

typically carries around 14,000 vehicles a day. Rottingdean is outside of

Brighton’s 2008 AQMA. Passive diffusion tube nitrogen dioxide monitoring has

been located in the village since January-2009. A Detailed assessment including



advanced dispersion modelling for air quality has been carried out for the village

and is presented in this report.

1.1.3 Preston Road-Preston Road junction and South Road to the Drove

This area is to the north of Brighton and north west of Preston Park. The closest

commercial and domestic properties are two metres from the kerb of Preston

Road (A23) which carries around 21,000 vehicles a day. South Road adjoins

near by and is one of the few crossing places under the main railway. When the

Brighton to Norwood railway was built in 1841 there was no need to provide a

wide bridge for passing travellers and farmers under the railway north of the town.

As the city had continued to expand South Road to The Drove has become an

important link from the east to the west across the urban area. The road under

the railway is narrow and steep. The Drove typically carries 12,750 vehicles a day

with a commercial and residential facade two metres from the kerb. Vans and

wider cars have to check their run on the hill climb and give way to oncoming

traffic. Preston Road and the Drove are not included in the 2008 AQMA.

Nitrogen dioxide has been monitored on this part of Preston Road since January

2009 and on the Drove since January 2012. A Detailed assessment for air quality

including an advanced dispersion for air quality has been carried out in this area

and the findings are presented in this report.

1.2 Purpose of Local Air Quality Management This report fulfils the requirements of the Local Air Quality Management process

as set out in Part IV of the Environment Act (1995), the Air Quality Strategy for

England, Scotland, Wales and Northern Ireland 2007 and the relevant Policy and

Technical Guidance documents. The LAQM process2 places an obligation on all

local authorities to regularly review and assess air quality in their areas, and to

determine whether or not the air quality objectives are likely to be achieved.

Where concentrations are likely to exceed, the local authority must declare an Air

Quality Management Area (AQMA) and prepare an Air Quality Action Plan

2 Currently under consultation so onus and quantity of duties falling on Local Authorities can be reduced and focus be directed towards further assessment and action planning rather than constant progress reporting



(AQAP) setting out the measures it intends to put in place in pursuit of the

objectives.

1.2.1 Reason for Detailed Assessments

The objective of this Detailed Assessment is to identify any areas that are outside

of the existing AQMA that are likely to have concentrations of nitrogen dioxide

above objective levels as stipulated in the air quality regulations, Table 1-1. The

previous Updating Screening Assessment report concluded that a detailed air

quality assessment for air quality was a statutory requirement for the areas

covered by this report. Given that monitoring and model methods are the same;

for simplicity the two separate detailed assessment areas have been included

within one report.

1.3 Air Quality Objectives

The air quality objectives applicable to LAQM in England are set out in the Air

Quality (England) Regulations 2000 (SI 928), The Air Quality (England)

(Amendment) Regulations 2002 (SI 3043), and are shown in Table 1.1. For

nitrogen dioxide the EU and English target concentrations are the same.

Table 1-1 Nitrogen Dioxide Air Quality Objectives Included in Regulations for the purpose of LAQM in England

Air Quality Objective Pollutant

Concentration Averaging Period 200 μg/m3 not to be exceeded more

than 18 times a year

1-hour mean Nitrogen dioxide

40 μg/m3 Annual mean

1.3.1 Discussion about Nitrogen Dioxide objectives

It is unlikely that the short term objective of 200 µg/m3 will be exceeded where the

annual mean is less than 60 µg/m3. The annual mean is a more stringent

objective that is more difficult to comply with. This detailed assessment considers

both objectives however the annual mean is likely to be the primary consideration

for permanent residential locations. Where a larger geographical area fails the



annual mean more people are likely to be effected. The amount of inhalation

dose and exposure to a mixture of pollutants are important when considering

impacts on cardio-pulmonary health. Pedestrians crossing the road, cyclists and

motorists using the road are not likely to be exposed to airborne pollution for the

same frequency and durations as a resident living adjacent to it.



2 Methodology

2.1 Monitoring Method

2.1.1 Diffusion Tubes

Nitrogen dioxide passive diffusion tubes have been placed on the façade of

buildings within five metres of the kerb. The sample tubes located in the detailed

assessment areas are part of a larger survey throughout Brighton and Hove.

Triplicate tubes are co-located with the continuous analyser (BH9) on

Beaconsfield Road. In accordance with the latest technical guidance any

difference in the reading of the continuous analyser and the co-located tubes is

used to apply an adjustment referred to as a bias correction factor for all the

tubes in the area. Table 1.2 Nitrogen Dioxide tube Bias correction factors in recent years

2007 2008 2009 2010 2011

0.72 0.72 0.84 0.85 0.82

Between 2007 and 2011 raw diffusion tube results have been on the high side

compared to local continuous analysers. The bias correction factor takes account

of this. The nitrogen dioxide diffusion locations in the two detailed assessment

area are included in Figure 2-1 and summarised in detail in Table 8-1. The

dispersion model has been set up to predict in space (but not the future)

concentrations at precisely the same location as the monitors. The comparison

between monitoring results and modelling estimations is used to verify the

dispersion model predictions. The model predictions are reported at virtual

receptors at roadside residential facades and as contour maps throughout the two

assessment areas.



Figure 2-1 Nitrogen Dioxide Monitoring in or adjacent to the Detailed Assessment Areas



2.1.2 Model Assessment Methodology

The impact of all emissions sources on local air quality in Rottingdean and near to

the Preston Drove Preston Road junction has been predicted using the

ADMS-urban (atmospheric dispersion model system). ADMS is used by the

Environment Agency and a number of larger local authorities to assess emissions

from traffic, commercial and domestic and industrial sources and their combined

impacts on local air quality. It is validated for the prediction of airborne pollution

dispersion. The model is developed and validated by CERC (Cambridge

Environmental Research Consultants)3. The ADMS model is set up to depict real

local conditions as closely as possible reflecting emissions to ambient air arising

from traffic and none traffic sources. The atmospheric emissions inventory toolkit

(EMIT also written by CERC) has been used to determine emissions from

commercial and domestic sources and different vehicle categories.

2.1.3 Model Approach - Year

2010 has been modelled to represent the current situation, not because this is the

most recent full year, but because monitoring throughout the city strongly suggest

2010 was a worse-case year for nitrogen dioxide concentrations during the past

decade. There has been little improvement in diesel emissions between Euro-I

and Euro V vehicles most especially in urban stop-start driving environments4. It

is recognised that some apparently rural villages for short distances have driving

conditions that might be described by the motor industry as ultra-urban.

Emissions are harder to predict in this scenario because internal combustion

engine performance is compromised by cold starts, idling, acceleration and

breaking. In recent years there has been a national and local shift towards

greater use of diesel vehicles that have higher emissions of NOx and particulate

compared with alternative modes of propulsion; including petrol5. Therefore it is

reasonable to assume as a worse case approach that similar roadside

concentrations to the 2010 scenario will be repeated during current and future

years up to and including 2015.

3 Cambridge Environmental Research Consultants CERC http://www.cerc.co.uk/environmental-software.html 4 Trends in NOx and NO2 emissions and ambient measurements in the UK, March 2011 http://uk-air.defra.gov.uk/reports/cat05/1103041401_110303_Draft_NOx_NO2_trends_report.pdf



2.1.4 Model Approach Emission Calculation

Traffic emissions are one of the most important variables for local air quality.

They and are influenced primarily by fuel type, vehicle mass and road gradient.

Speed is used with EMIT to determine emissions for each road section and the

slowest speeds represent the highest tail pipe releases of oxides of nitrogen NOx.

For internal combustion engines it is reasonable to assume the slowest speeds at

around 5 to 10 kph (<10 mph) will produce the highest emissions. In reality

emissions will be influenced by driving style, the degree to which the driver

conserves momentum (kinetic energy) and the rate of acceleration. Fuel demand

and emission rates relate to the actual forces a vehicles needs to overcome to

propel forward, something that is best explained by Vehicle Specific Power (VSP)

Figure 2-2 Vehicles Specific Power relates to emission rates

Courtesy of David Carslaw, London Air Quality Network Seminar 2011.

2.1.5 Model Approach - after emission variables Road width (kerb to kerb distance) and street canyon width (building-line façade

to façade distance) strongly influence dilution and dispersion of emission and

concentrations in the near field within fifteen metres of the traffic sources.

In close proximity to the traffic other variables are less influential on local air

quality such as background concentrations that would prevail if the road was not

5 Brighton and Hove City Council, 2012 Updating Screening and Assessment



there and the choice of meteorological data used to determine dispersion in the

short distance between the tail-pipe and roadside i.e. residential (pathway). One

argument is that meteorological conditions are more influential over longer

pathways between source and receptor for example a plume emitted from a

power station. In Brighton and Hove the NO2 problem where people live and are

present for longer durations is almost entirely within ten metres of a road kerb.

The model predicts nitrogen dioxide concentrations at building-line façades at

monitoring locations and also at selected residential receptors closest to the road.

The receptor details for the Preston Road area are given in and for Rottingdean in

Figure 8-1 and Figure 8-2.

2.1.6 Traffic Data

Detailed traffic data has been obtained from continuous counters. The weight

sensitive strips operate twenty-four hours a day, seven days a week and count

five categories of vehicle as follows:

• Motorcycles or two wheel powered (2WP) vehicles

• Cars

• Light Goods Vehicles (LGV < 3.5 tonnes) – typically vans and minibuses

• Heavy Goods Vehicles (HGV rigid and articulated)

• Buses and Coaches

The traffic counters that provide evidence in support of the Rottingdean detailed

assessment are:

• Site 23 A259 between Roadean and Greenways

• Site 614 A259 Marine Drive west of Chailey Av

• Site 617 B2123 Falmer Road, Woodingdean - Rottingdean

Information on the locations is given in the appendix, Figure 8-3. Similarly for

Preston Drove-Preston Road and South Road data from one continuous counter

and two 12-hour manual counters were used:



• Site 50 A23 Preston Road South of Preston Drove

• M4857 Preston Drove west of five ways

• A704 South Road between the A23 and the railway

An adjustment with an increase of 1 % for each year has been applied where

available traffic counts refer to previous years prior to 2010. This approach is

similar to past detailed assessments in Sussex and elsewhere. Whilst the model

is set up to reflect the real world as closely as possible the approach is likely to

represent a worse case. After a long term trend for increases in traffic since the

Second World War some local road counters show that the traffic numbers

peaked around 2007/08 time. Local fuel consumption statistics, point to a decline

in personal vehicle use since 20085. At the same time petrol consumption

appears to be lower than a few years ago and diesel has a greater share of the

private van and car market. The count of diesels is likely to be more influential on

roadside air quality than the total tally of traffic.

Using knowledge of the local area the proportion of cars that are taxis for each

road link has been estimated. The HGV component has been divided into six

groups; three rigid and three articulated categories using the following percentile

splits obtained from CERC.

Rigid HGV: 2 axle: 56.2% 3 axle: 7.4% 4 axle: 9.4% Articulated HGV: 4 axle: 5.0% 5 axle: 12.1% 6 axle: 9.9%

This approach provides eleven vehicle categories each with their own emissions

profiles. A full list of Traffic counts is given in Table 8-4 and Table 8-5.

2.1.7 Traffic Speed

Each road link in the two detailed assessment areas is assigned a representative

speed (kph) that relates to the busiest hours in the day i.e. modal average when

the majority of vehicles travel at peak hours. Low speeds are assumed in order to



calculate realistic emission rates. This worse case approach helps the model

achieve a closer agreement with recent roadside monitoring without the

requirement for further adjustments. The physical parameters of each road link

included in the two detailed assessment areas are tabulated in Table 8-6 and

Table 8-7.

2.1.8 Road Width

As stated above road width can be a significant variable for localised air quality.

Where relatively few internal combustion engines operate in narrow and confined

spaces airborne pollution usually becomes more concentrated than the

surrounding environment. The carriageway widths included in this model

assessment vary from between 5 metres along the middle section of Rottingdean

High Street, up to 18m on the A259 near St Dunstan’s roundabout. South Street

as it approaches The Drove under the railway is confided to less than 6 metres

for east and westbound traffic. The narrow carriageways started as cart tracks

and livestock drives, in contrast wider road widths where purpose built for

monetised vehicles.

2.1.9 Road Gradient

The road links included have variable gradients and some sections have steep

inclines. Steeper roads demand more fuel to shift a vehicle’s mass on a climb

and this scenario usually results in higher tail-pipe emissions. Higher ambient

concentrations of pollutants close to the kerb are likely to arise where engines

haul heavy vehicles on a hill climb. The effects of the climb may be compounded

where the road link is enclosed by buildings adjacent to the slope.

Road slopes have been calculated using road spot heights on detailed OS maps

to derive a ratio of so many metres up (Z) to so many along (X or Y). For

example a 1:15 gradient on a busy road is likely to be influencing factor on air

quality adjacent to the kerb. Road gradient is one of the variables computed with

vehicle category, count and speed that have been used to derive emission rates

for each road sections.



2.1.10 Emission Factors

Emissions have been calculated using EMIT for each of the road links in the two

detailed assessment areas. The emission rates for each road section are set out

from Table 8-8. Two methods for calculating emission were compared. The

worse-case approach for oxides of nitrogen is to assume all diesel vehicles have

Euro-1 engines in accordance with CERC methods employed; 2010-2012.

Depending on other variables this gives emission rates for NOx that are between

1.6 and 3.3 times higher. Assuming euro-1 for diesel primary NO2 emission is

almost six times greater than standard emission assumptions. Using this

approach the primary NO2 ranges from between 29 to 36% for each road link.

Whilst we know that almost all local lorries, buses, taxis and vans run on diesel

we may have under estimated the number of private cars that run on diesel - now

thought to be between 50 and 60% of the total.

When the model is run assuming all diesels as euro-1 predictions show an

excellent agreement with recent monitoring results and the pollution contour

maps are closer to those expected especially in the area of interest within ten

metres of transport corridors.

The emission rates are influenced by all of the variables listed above. Each road

link is defined by a change to one of the parameters for example tally of traffic

(car, van or bus) street gradient or a different degree of building enclosure

adjacent to the road.

2.1.11 Street Canyons

Where road sections are enclosed by buildings close to the kerb separated by a

narrow pavement the scenario is often referred to in air quality terms as a street

canyon. As with natural canyons enclosed man made canyons in the built realm

can have micro-climates with different air flows and sunshine hours compared to

the plane above. Some of the road links listed have been characterised as street

canyons in order represent the influence of road enclosure on the dispersion of

emissions from vehicle tail-pipes.

2.1.12 Selected Model Receptors

A series of discrete receptors have been selected at the building-lines of

residential properties parallel with the road sources to be included as



interrogation points in the model. Figure 8-1 and Figure 8-2 depicts the location

of these receptors that complement the real diffusion tube localities listed in Table

8-1.

2.1.13 Industrial Sources

No large chimneys are included in the model set-up. Brighton and Hove is not a

heavily industrialised area and the Shoreham power station is deemed to be

sufficient distance not to warrant specific inclusion with either of the detailed

assessment areas.

2.1.14 Commercial and Domestic Emissions

All other emission sources are included in the model as area sources this

includes domestic and commercial sources such as home and business heating,

minor roads and industrial processes. 16 km2 of grid sources are surround the

detailed assessment area for Preston Road and 45 km2 around Rottingdean

either including sources in the adjacent local authority of Lewes District Council.

It is likely that background sources have been over estimated in the model and

actual concentrations away from roads are likely to be slightly lower than those

reported for example at Roadean School.

2.1.15 Ambient Background Levels

Regional background concentrations in the model derive from the Automatic

Urban Rural Network (AURN) continuous analyser at Lullington Health in East

Sussex. The regional background represents concentrations that would

hypothetically prevail if the urban area was subtracted. Generally 2010 had

higher background concentrations compared with 2009 and 2011. For example

the following background data is included as part of the model input:

Nitrogen Dioxide NO2 12.6

Nitrogen Monoxide NO 9.7

Ozone O3 58.8



2.1.16 Chemistry

The chemical reaction scheme within the ADMS-urban model has been used to

calculate the chemical reactions in the atmosphere between nitric oxide (NO),

nitrogen dioxide (NO2) ozone (O3) and free radical VOC (Volatile Organic

Compounds). Eight standard photochemical reactions are included. Due to

photochemical reactions near ground level ozone tends to be more concentrated

in the spring and summer and this can have some influence NO2 levels.

2.1.17 Meteorological Data

Hourly sequential meteorological data from Shoreham-by-Sea for 2010 has been

used to assess dispersion of emission in the model. The dispersion model

requires the following meteorological parameters:

Year (not a leap) 2010

Julian Day, 1-365

Hour of Year 1-8760

Wind speed m/sec

Wind Direction 0-360°

Relative Humidity %

Temperature °C

Cloud Cover Oktas 1-8

Data from Gatwick for the same calendar year has also been used as a

comparison with interesting findings, discussed in paragraph 3.2.1. Wind Rose

diagrams show the annual distribution of wind velocities from Shoreham-by-Sea.

2.1.18 Time Varying Emissions

Traffic emissions rates are based on daily traffic counts. That said the model

acknowledges that emissions from traffic are not equal for every hour midnight to

midnight. Within a 24-hour period the tally of traffic has a high degree of

deviation compared with the mean and this pattern varies between transport

corridors. Brighton has an active night time economy and a significant proportion

of traffic especially buses and taxis happen during the night or shortly after

licence premises close. As shown in the typical local traffic distribution



Figure 2-3. Partly to avoid other road users large articulated lorry deliveries can

arrive at five and six in the morning.

Figure 2-3 Twenty-Four hour Traffic Variability A259 Brighton

Diurnal Traffic Variation

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 3 6 9 12 15 18 21 24

Hours in the day

Percen

tile Propo

rtion

Sat

Sun

Weekday

The distribution is from the A259 which passes through Rottingdean. The pattern

derives from a seven day count approximately 3 km further west nearer to the

centre of Brighton. Whilst the week day commuter patterns are comparable the

counts are likely to be more skewed towards the night compared with

Rottingdean village. This is likely to represent worse-case. If bus, taxi and truck

emissions occur in the night this is likely to be less favourable for dispersion. At

night atmospheric conditions are more likely to be stable, the layered nature of

the air lacks convective, thermal lift and low level inversions can trap ground level

emission sources. Local coastal breezes also have less influence in mid-winter

and at night.

2.1.19 Latitude and Sunlight

Brighton has latitude of: 50.8 °N and the standard model set-up has been altered

to reflect the actual local latitude. Throughout the year noon time sun climbs to a

higher azimuth in the sky compared to further north. In comparison with the

majority of the British Isles the south coast of Sussex receives more hours of

sunshine. This relates to the cloud cover parameter in the hourly sequential



meteorological data. Summer sunshine is likely give rise to greater incidence of

thermals and convective movements in the lower atmosphere (troposphere). This

may be advantageous for vertical dispersion in the summer in combination with

sea to land breezes. Sunlight also creates a photochemical reaction that

produces ozone in the troposphere that can influence the amount of NO

conversion to NO2. In theory the hours of strong light at roadside may influence

the rate at which NO emissions convert to NO2 in ambient air. Tall street canyons

influence wind velocities in the urban realm and can also shade streets potentially

altering the rate of photochemical reactions at roadside. Local monitoring records

consistently show higher ambient NO26 between November to February and this

usually raises the annual average.

2.1.20 Local Surface Parameters

A surface roughness figure is included to consider how air flows over different

surfaces for example ice provides less resistance than a city. Surface albedo is

considered in the model and is defined at the ratio of reflective to shortwave

incoming radiation. The Albedo varies with land type. The Monin-Obukhov

length is a factor used to account for the heat produced by urban areas. Man

made heat can potentially disrupt stable atmospheric conditions that would

normally prevail at night. The selected values represent a small urban area with

some fields and open spaces.

2.1.21 Model Performance and Uncertainty

Dean literally means valley and Rott, leader or people. The periglacial valley and

surrounding topography provided some degree of natural shelter from the

strongest winds providing a natural haven for the ancient settlement and passing

ships. Wind speeds are often likely to be lower than elsewhere along the coast a

local condition probably appreciated by ancient settlers 4,000 years ago. The

village sits in a natural cleft in the topography a situation that is less favourable for

dispersion of emissions from fires, chimneys and vehicle tail pipes. However

because the residential localities of interest for air quality are so close to traffic

sources meteorology and topography are not likely to be the principal variables.

The model does not take account of coastal and topographical effects on wind

6 An ambient concentration differs considerably from an emission discharge from an exhaust pipe or chimney



velocities. It does not predict future air quality – all of these options would

considerably increase the level of model uncertainty and confidence in

predictions. Section 3.2.1 discusses sensitivity analysis, followed by verification

of model predictions compared with façade monitoring.



3 Results

3.1 Monitoring Results

3.1.1 Model Verification

In order to verify model predictions results have been compared with annual

monitoring data. Due to the thorough consideration of all parameters in the

previous chapter the model estimations show excellent agreement with the all the

monitors shown in Figure 2-1 Therefore no adjustment is required in accordance

with the methods set out in LAQM Technical Guidance TG (09). CERC note 89

(2010) refers to the method of adjusting NOx emissions vehicles to Euro-1 and

post dates TG 09. The modelling and monitoring results are compared in Table

8-10 and Table 8-11.

3.2 Results of Modelling Predictions

3.2.1 Sensitivity Analysis

Sensitivity analysis suggests that meteorological data is not the primary variable

where residential receptors are in very close proximity to emission sources, for

example in Rottingdean High Street and The Drove near the bridge under the

railway. In order to interrogate the meteorological variable hourly sequential data

(2010) from Gatwick has been compared with Shoreham-by-Sea. The finding

show that Gatwick air flows and conditions are slightly less favourable scenario

for dispersion compared with the near-coastal site at Shoreham. In theory the

model sensitivity suggest that if wind speeds were lower as they are for more

hours of the year inland, pollution levels could be higher for. Air Monitors suggest

that 2010 was a worse case year for airborne nitrogen dioxide. This challenges

previous model assumptions which assumed year on year improvements for air

quality. Fresher winds from the English Channel and Atlantic help dilute local

airborne pollution; however this does not happen for all the hours in the year.

Wind Rose patters from Shoreham for 2008 and 2010 are shown in Figure 8-5.

Uncommon wind speeds and still conditions that can happen for 20 or 25% of the

year are likely to be more significant for airborne pollution than the stronger

prevailing winds which helps replenish local air quality.



3.2.2 Results at Receptors

Model predictions for the selected residential receptors are presented in Table

8-12 and Table 8-13. The highest concentrations of NO2 are found closest to the

kerb in confined spaces or on hill climbs. The highest traffic counts do not always

give the highest ambient pollution concentrations where people live.

3.2.3 Contour Map Results

The maps presenting model prediction are shown from Figure 8-6. There is a high

level of scientific confidence that nitrogen dioxide exceeds the EU and English

limit values within three to five metres of road kerbs at:

• The junction of Preston Drove and Preston Road,

• The hill climb of The Drove

• Rottingdean High Street.

3.3 Discussion of Results

Concentrations drop off with distance back from road sources. Road slopes and

street canyons also influence the distribution and concentrations of pollutants.

The total tally of traffic is not as significant as the degree to which road links are

confined, the number of heavier or more powerful diesel vehicles and the driving

style in each road link for example repeated rapid acceleration, idling engines in

one place for longer durations.

Usually facades in close proximity to the road are exposed to higher

concentrations. Although traffic counts are highest for the A259 pollution is not

the highest. This is because residences are set back from the road. The extra

space allows for better ventilation and air entrainment over more hours of the

year.



4 Conclusions LAQM reports show that the problem of poor air quality arises because of internal

combustion engines in confined spaces. It is less dependent on the total count of

traffic as relatively few vehicles can cause a breach of the air quality limits where

roadside space is limited. This report shows examples of how a road link with

approximately 13,500 vehicles a day can give higher emissions than a road link

with 25,000 vehicles a day. Important variables to consider are the uninterrupted

flow of the traffic, the count of diesel vehicles, road gradient the power of engines

– driving style and the number heavy vehicles. Furthermore dispersion of the

quoted emission rates (tonnes per year) will be influenced by building enclosure

surrounding the road carriageway. The outdoor pollutant concentration (g/m3 of

air) that people inhale over longer durations is a function of both tail pipe

emissions and ambient dispersion.

Over recent years it is evident air quality action plan policies such as; modal

transport shift, better public transport, more walking and cycling, 20 mph speed

limits and high parking charges alone will not eradicate failure to comply with

nitrogen dioxide limits at all locations. Shift from petrol to diesel is the most

pronounced change in travel since 2005 and this is not a beneficial trend for air

quality adjacent to slow roads. The dash for diesel is not driven by government

policy but by economic market considerations.



5 Future Work and Recommendations

Following two detailed assessments the City Council has legal responsibility to

review its existing Air Quality Management Area (AQMA). The review must

redefine the AQMA to include the new areas identified by this report. The next

steps in the LAQM process are as follows:

• Further Assessment dispersion model to justify changes to the AQMA to

consider Portslade, Central Brighton and Rottingdean

• New AQMA map to be agreed by elected members

• Further Assessment model with source apportionment i.e. what sources

(lorry, truck, bus taxi or car) cause the airborne pollution to exceed limits

adjacent to various road links included within the new AQMA.

• 2013 action plan with traffic and none traffic measures to improve air

quality throughout the city with priority focus on the new AQMA.

• New air quality action plan policies for the city

• Recommendations on more effective air quality action plans to UK

Government



6 Action Plan Options The previous section outlines how determining the contribution to pollution from

various vehicle categories will help to justify future measures in the air quality

action plan. With a view to action local residents have suggested the following

options to minimise airborne pollution in Rottingdean:

• One way traffic along the High Street with northbound traffic via an

alternative route with a wider street and carriageway for example Steyning

Road and Chailey Avenue.

• Restriction to Heavy Vehicles The proposed Rottingdean neighbourhood

plan7 requires a weight limit of 7.5 tonnes on vehicles through the High

Street. This is unlikely to include double-decker buses at nearly 12 tonnes.

• A by-pass around the village Rottingdean is surrounded by the South

Downs National Park so options for a new road are very limited. A by-pass

could improve airborne nitrogen dioxide, particulate and noise in the centre

of the village. A new road risks interruption to the serenity and tranquillity

of surrounding countryside and other homes. Additional fuel consumption

and CO2 emissions would result if vehicles have to drive further to get to

their destinations (even if this reduced journey times with faster speeds).

The community have identified an alternative route for the B2123 to the

north with traffic via Warren Road and Warren Avenue.

• A tunnel - although tunnel building is not as common in the UK as in many

Alpine countries costs have come down. If the B2123 was tunnelled for a

short distance of 600-850m (estimated at £30 to £42 million) the historical

character of the High Street could be restored without need to

accommodate through traffic. Further information is presented in the AA

report8

7 The Parish Council’s Consultation Document for the Production of Rottingdean Neighbourhood Plan 2012 8 AA Going Underground TUNNELS: what role in Town and Country? http://www.theaa.com/public_affairs/reports/going_underground.pdf



7 References 1 Reference to the 2011 Census Results http://www.brightonbusiness.co.uk/htm/ni20120717.660827.htm 2 Cambridge Environmental Research Consultants CERC http://www.cerc.co.uk/environmental-software.html 3 Trends in NOx and NO2 emissions and ambient measurements in the UK, March 2011 http://ukair.defra.gov.uk/reports/cat05/1103041401_110303_Draft_NOx_NO2_trends_report.pdf 4 Brighton and Hove City Council, 2012 Updating Screening and Assessment http://www.brighton-hove.gov.uk/index.cfm?request=c1001183 5 AA Going Underground TUNNELS: what role in Town and Country? http://www.theaa.com/public_affairs/reports/going_underground.pdf 6 The Parish Council’s Consultation Document for the Production of Rottingdean Neighbourhood Plan 2012

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